c2c: cross-cluster replication view in DB Console is visible to non-admins

**Describe the problem**

The ‘Cross-cluster replication’ screen is visible to non-admins. (The navigation is correctly removed.)

**To Reproduce**

- Log in as admin.
- Navigate to Metrics → Cross-cluster replication
- Revoke admin rights on user
- Reload the above DB Console page
- The metrics still display, though the navigation shows blank

**Expected behavior**

The page should show an error message indicating insufficient rights, as other pages around the DB Console do for non-admins.

In fact, I don’t think we should hide the nav item in the pull-down at all. Users should be allowed to navigate to it (know it exists) but get an error message.

**Environment:**
v23.1.5
Mac Intel
Install via homebrew

Jira issue: CRDB-29527